In radar systems, an electromagnetic wave may propagate radially outwards from a transmitter over a continuum of azimuth values. Reflection occurs when a ray encounters a surface (e.g., a side of a building or a target) and leaves the surface in a different direction, in which the angle of incidence equals the angle of reflection. For simplicity, all rays are taken to lie in two horizontal dimensions x and y, with all reflecting surfaces perpendicular to the x-y plane. The azimuth of a Cartesian vector (rx, ry) is defined to be equal to sin−1(rx/√{square root over (rx2+ry2)}). Without this simplification, the claims herein are readily extensible to ray traces in three dimensions with the inclusion of an elevation angle. Here, the electromagnetic waves traveling from a transmitter and arriving at a point in space (e.g., a sensor) may have traveled along multiple different ray paths. Since rays emanating from a transmitter at a given time may have taken different paths, the rays may arrive at the sensor at different points in time, with different amplitudes, and/or with different angles of arrival.
The multipath rays emanating from a transmitter and reflecting from a target may reach the target directly or after one or more reflections. Further, multipath rays reflecting from a target and arriving at a sensor may reach the sensor directly or after one or more reflections. Reflected rays include those rays that have undergone one or more reflections off vertical surfaces (e.g., sides of buildings) along their paths from transmitter to target and then from target to sensor.
Sense Through the Wall (STTW) radar performance for moving target detection and location is limited by the severe multipath environment found in urban structures. Subsequently, a wide range of applications that could benefit from improved target location techniques, such as emergency services, tracking people, and military environments.